Acoustic tagging seeks answers to King salmon decline
Jeff Richardson
907-474-5350
Oct. 14, 2025
An ambitious new research project is aiming to better understand the lives of king salmon by focusing on their difficult journey from freshwater habitat to the ocean.
A newly captured juvenile king salmon rests in a viewing box container, which allows researchers to identify fish species and measure their size.
The project, a collaboration between the 窪蹋勛圖厙 and Alaska Department of Fish and Game, is using hundreds of acoustic tags and an array of underwater hydrophones to track young salmon as they navigate the Kenai River to Cook Inlet.
Researchers are focusing on kings in the smolt stage, a relatively understudied period of development. Resources for studying king salmon have largely focused on adult fish.
The project comes amid widespread declines among Alaska king salmon populations, and the Kenai Rivers famous run has become the poster child for the struggles of the species, said Andy Seitz, a professor at the UAF 窪蹋勛圖厙 of Fisheries and Ocean Sciences. Knowing more about the perils facing juvenile salmon could spotlight the challenges they are facing.
Its a time when theyre going through physiological changes, and its also a dangerous stage, said Seitz, who is co-leader of the project. Theyre changing from freshwater to saltwater fish, and there are a lot of hungry mouths in the ocean.
A research team recently concluded the first season for the project by implanting 289 Kenai River king salmon smolt with tiny devices about the size of a Tic Tac mint that emit regular pings. Each has a unique signal, allowing researchers to identify individual fish with underwater hydrophones as they make their journey in the Kenai River to Cook Inlet.
The most notable array of sensors is a roughly 4-mile-wide span near the mouth of the Kenai, which researchers plan to double in size next year. It will monitor tagged fish during a critical stage when they depart their freshwater habitat.
An acoustic receiver rests on the shore of the lower Kenai River during low tide. The receivers are used to monitor tagged salmon as they migrate to Cook Inlet.
The acoustic technology has never been used on juvenile salmon in Alaska, and the first summer was spent working to adapt it to the rugged Kenai River environment. CFOS students working on the tagging project include Johnna Elkins, Dakota Rygh and Danielle Tryon. Elkins and Tryon are also ADFG employees.
The project will expand in scope as it continues for each of the next two summers.
A better understanding of the survival bottlenecks facing young salmon could ultimately affect how they are managed in Alaska rivers, said Tony Eskelin, a Soldotna-based fisheries biologist who is leading the project for ADFG.
Transitioning into the marine environment is a perilous life stage for these fish, he said. If we can better understand factors affecting their survival, maybe we can make some decisions to help them along the way.
We have a lot of excitement for this project, and a lot of data to process.
The project is being funded by a $4 million federal earmark through NOAA to research juvenile Chinook salmon.
ADDITIONAL CONTACTS: Andy Seitz, acseitz@alaska.edu; Tony Eskelin, anthony.eskelin@alaska.gov
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